The present invention relates to the mechanism for changing inductance of a push-button type tuner, more specifically to a mechanism for changing inductance of a tuner which is so constructed to be compact and flat in size as to be adapted for use with a tape recorder.
Conventionally, in push-button type tuners of the kind designed for installation in motor vehicles, there are provided a plurality of stationary coils and a similar number of tuning cores which are mounted on a core carriage and movable in and out of coil bodies to change inductance by a selective depression of push-button through a rotatable treadle-bar assembly and an additional manual tuning mechanism having a manually operative tuning shaft adapted to be rotated to change the inductance. In such a conventional tuner there is a metal mounting bracket which is rectangular in shape. The bracket comprises vertical side walls arranged in parallel, and vertical front and rear walls arranged in parallel and intersecting the side walls at right angle.
A push-button assembly is provided with a button plate slidably positioned through the front and the rear walls by means of biasing force of a coil spring mounted on the end thereof and with a crescent-shaped channeling plate retainable at a desired position thereupon. A comb-shaped rotary member is rotatably supported on the side walls by means of a horizontally extending shaft, and usually the teeth of the rotary member are located in a slightly frontwardly tilted position close to the front wall and are ready to touch depending projections disposed on the push-button.
A treadle-bar assembly is rotatably supported on the pair of vertical side walls by means of two shafts fixed to and extending from a pair of flat support members, to the inside of which are fixed a pair of parallel rods. With the forward advancement of the push-button, the crescent-shaped channeling plate is also advanced to collide with the pair of parallel rods of the treadle assembly, whereby the rotation angle of the treadle-bar assembly is set corresponding to the position of the channeling plate retained at a desired angle.
A manually operative shaft for a clutch mechanism is also mounted on the front side wall in a usual manner. The rotation of the treadle-bar assembly permits the core carriage on which cores are mounted to shift forward or backward whereby the cores are movable in and out of the coil body with the resultant changing of inductance as desired. However, this type of prior ones are fairly bulky and have not been preferable when arranged in combination with other machinery. Naturally it is almost impossible to reduce a physical thinness of the tuner as to be adapted for use in combination with a tape recorder.
Recent market situation presents us that there may be a considerable demand for tape recorders provided with a push-button tuner. Naturally, various types of mechanism available to meet the demand are now being searched, which requires such a type of tuner as having an optimum physical thinness to be compatible with the tape recorders.
It is an object of the present invention to provide a tuning mechanism which is so designed as to have an optimum thinness, which is flat in shape but capable of maintaining a correct tuning.
It is another object of the invention to provide a push-button mechanism which permits a smoother but accurate function of the flat type tuner.
It is still another object of the invention to provide a pair of cam plates alternatingly slidable with each other which is so constructed as to shift a core carriage whereby cores mounted thereon go in and out of a corresponding coil body so that a correct tuning may be performed.
It is a further object of this invention to provide a simple declutch mechanism equipped with lever means which performs a smooth and accurate declutching operation of a push-button type tuner.
Other and further objects, features and advantages of the invention will appear more fully from the following description.